DESCRIPTION

Blowfish is a block cipher that operates on 64 bit (8 byte) blocks of data.
It uses a variable size key, but typically, 128 bit (16 byte) keys are
considered good for strong encryption. Blowfish can be used in the same
modes as DES (see des_modes(7)). Blowfish is currently one
of the faster block ciphers. It is quite a bit faster than DES, and much
faster than IDEA or RC2.

Blowfish consists of a key setup phase and the actual encryption or decryption
phase.

BF_set_key() sets up the BF_KEYkey using the len bytes long key
at data.

BF_ecb_encrypt() is the basic Blowfish encryption and decryption function.
It encrypts or decrypts the first 64 bits of in using the key key,
putting the result in out. enc decides if encryption (BF_ENCRYPT)
or decryption (BF_DECRYPT) shall be performed. The vector pointed at by
in and out must be 64 bits in length, no less. If they are larger,
everything after the first 64 bits is ignored.

The mode functions BF_cbc_encrypt(), BF_cfb64_encrypt() and BF_ofb64_encrypt()
all operate on variable length data. They all take an initialization vector
ivec which needs to be passed along into the next call of the same function
for the same message. ivec may be initialized with anything, but the
recipient needs to know what it was initialized with, or it won't be able
to decrypt. Some programs and protocols simplify this, like SSH, where
ivec is simply initialized to zero.
BF_cbc_encrypt() operates on data that is a multiple of 8 bytes long, while
BF_cfb64_encrypt() and BF_ofb64_encrypt() are used to encrypt an variable
number of bytes (the amount does not have to be an exact multiple of 8). The
purpose of the latter two is to simulate stream ciphers, and therefore, they
need the parameter num, which is a pointer to an integer where the current
offset in ivec is stored between calls. This integer must be initialized
to zero when ivec is initialized.

BF_cbc_encrypt() is the Cipher Block Chaining function for Blowfish. It
encrypts or decrypts the 64 bits chunks of in using the key schedule,
putting the result in out. enc decides if encryption (BF_ENCRYPT) or
decryption (BF_DECRYPT) shall be performed. ivec must point at an 8 byte
long initialization vector.

BF_cfb64_encrypt() is the CFB mode for Blowfish with 64 bit feedback.
It encrypts or decrypts the bytes in in using the key schedule,
putting the result in out. enc decides if encryption (BF_ENCRYPT)
or decryption (BF_DECRYPT) shall be performed. ivec must point at an
8 byte long initialization vector. num must point at an integer which must
be initially zero.

BF_ofb64_encrypt() is the OFB mode for Blowfish with 64 bit feedback.
It uses the same parameters as BF_cfb64_encrypt(), which must be initialized
the same way.

BF_encrypt() and BF_decrypt() are the lowest level functions for Blowfish
encryption. They encrypt/decrypt the first 64 bits of the vector pointed by
data, using the key key. These functions should not be used unless you
implement 'modes' of Blowfish. The alternative is to use BF_ecb_encrypt().
If you still want to use these functions, you should be aware that they take
each 32-bit chunk in host-byte order, which is little-endian on little-endian
platforms and big-endian on big-endian ones.

RETURN VALUES

None of the functions presented here return any value.

NOTE

Applications should use the higher level functions
EVP_EncryptInit(3) etc. instead of calling the
blowfish functions directly.